Research Papers: Power Engineering

Fouling Formation in 575 MV Tangential-Fired Pulverized-Coal Boiler

[+] Author and Article Information
E. Bar-Ziv1

 Ben-Gurion University, P.O. Box 653, Beer-Sheva 84105, Israelbarziv@bgu.ac.il

Y. Berman, R. Saveliev, M. Perelman, E. Korytnyi, B. Davidson

 Ben-Gurion University, P.O. Box 653, Beer-Sheva 84105, Israel

B. Chudnovsky

 Israel Electric Corporation, P.O. Box 10, Haifa 31000, Israel



Corresponding author.

J. Eng. Gas Turbines Power 132(12), 123001 (Sep 01, 2010) (7 pages) doi:10.1115/1.4001297 History: Received December 10, 2009; Revised December 17, 2009; Published September 01, 2010; Online September 01, 2010

Due to the liberalization of the energy markets and the globalization of coal procurement, fuel management became of substantial importance to power plant operators, which are faced with new challenges when operating with coal types different from the originally designed ones for the specific boiler. Environmental regulations, combustion behavior, possible malfunctions and low operation, and maintenance cost became of essential importance. Fouling is one of the major challenges when new coals are being used. For that purpose we initiated a comprehensive study of fouling on the water-wall tubes in a 575 MW tangential-fired pulverized-coal utility boiler. We developed a methodology to evaluate fouling propensity of coals and specifically tested two bituminous South African coals: Billiton-Prime and Anglo-Kromdraai. The methodology is based on the adherence of ash particles on the water walls. Adherence of the ash particle depends on the particle properties, temperature, and velocity vector at the boundary layer of the water walls. In turn, the flow and temperature fields were determined by computational fluid dynamics (CFD) simulations. For CFD simulations we also needed the combustion kinetic parameters, emissivity, and thermal resistance, and they were all determined experimentally by a 50 kW test facility. Using this methodology we mapped off the locations where fouling is mostly to occur. It was found that our results fitted with the experience from the data obtained for these two coals in the Israel Electric Corporation utility boilers. The methodology developed was shown to be able to provide the fouling propensity of a certain coal, and yielded good prediction of the fouling behavior in utility boilers. Therefore, the methodology can assist in the optimization of the soot-blowing regime (location and frequency).

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Schematics of (a) the radial cross section (top view) of the probe and the furnace, and (b) the axial cross section (side view) of the probe and the furnace (TC denotes thermocouple)

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Figure 2

Coal/ash particles in the water-wall boundary layer

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Figure 3

Kinetic model for the devolatilization and combustion of coal

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Figure 4

Photographs of the probe with the ash deposit and SEM analyses of the deposit of AKD and Billiton-prime coals after 150 min from the insertion of the probe into the furnace at l/d=7.83

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Figure 5

Experimental results for the water-wall tube heat absorption versus time for the Billiton-Prime and AKD coals

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Figure 6

Rate of heat absorption loss versus time for coals AKD (black) and Billiton-Prime (dashed black)

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Figure 7

Heat flux prediction (top) and measurement (bottom) at the front and right walls of the tangential-fired boiler for different resistances (left: clean furnace (R=0.002 m2 K/W−1), right: dirty furnace R=0.0038 m2 K/W−1 when the Biliton-Prime coal was burned. The predictions were done using operation parameters in Tables  45, and the model parameters from Tables  67.

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Figure 8

Localized ash deposition rate (mass) on the front wall tangential-fired boiler



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